Commit 34f7c96d authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

objtool: Optimize !vmlinux.o again 



When doing kbuild tests to see if the objtool changes affected those I
found that there was a measurable regression:

          pre		  post

  real    1m13.594        1m16.488s
  user    34m58.246s      35m23.947s
  sys     4m0.393s        4m27.312s

Perf showed that for small files the increased hash-table sizes were a
measurable difference. Since we already have -l "vmlinux" to
distinguish between the modes, make it also use a smaller portion of
the hash-tables.

This flips it into a small win:

  real    1m14.143s
  user    34m49.292s
  sys     3m44.746s

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Reviewed-by: default avatarAlexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200416115119.167588731@infradead.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c4a33939

tools/objtool/elf.c

+43 −19
Original line number Diff line number Diff line
@@ -27,6 +27,22 @@ static inline u32 str_hash(const char *str) 
	return jhash(str, strlen(str), 0);

}



static inline int elf_hash_bits(void)

{

	return vmlinux ? ELF_HASH_BITS : 16;

}



#define elf_hash_add(hashtable, node, key) \

	hlist_add_head(node, &hashtable[hash_min(key, elf_hash_bits())])



static void elf_hash_init(struct hlist_head *table)

{

	__hash_init(table, 1U << elf_hash_bits());

}



#define elf_hash_for_each_possible(name, obj, member, key)			\

	hlist_for_each_entry(obj, &name[hash_min(key, elf_hash_bits())], member)



static void rb_add(struct rb_root *tree, struct rb_node *node,

		   int (*cmp)(struct rb_node *, const struct rb_node *))

{
@@ -115,7 +131,7 @@ struct section *find_section_by_name(struct elf *elf, const char *name) 
{

	struct section *sec;



	hash_for_each_possible(elf->section_name_hash, sec, name_hash, str_hash(name))

	elf_hash_for_each_possible(elf->section_name_hash, sec, name_hash, str_hash(name))

		if (!strcmp(sec->name, name))

			return sec;
@@ -127,7 +143,7 @@ static struct section *find_section_by_index(struct elf *elf, 
{

	struct section *sec;



	hash_for_each_possible(elf->section_hash, sec, hash, idx)

	elf_hash_for_each_possible(elf->section_hash, sec, hash, idx)

		if (sec->idx == idx)

			return sec;
@@ -138,7 +154,7 @@ static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx) 
{

	struct symbol *sym;



	hash_for_each_possible(elf->symbol_hash, sym, hash, idx)

	elf_hash_for_each_possible(elf->symbol_hash, sym, hash, idx)

		if (sym->idx == idx)

			return sym;
@@ -205,7 +221,7 @@ struct symbol *find_symbol_by_name(struct elf *elf, const char *name) 
{

	struct symbol *sym;



	hash_for_each_possible(elf->symbol_name_hash, sym, name_hash, str_hash(name))

	elf_hash_for_each_possible(elf->symbol_name_hash, sym, name_hash, str_hash(name))

		if (!strcmp(sym->name, name))

			return sym;
@@ -224,7 +240,7 @@ struct rela *find_rela_by_dest_range(struct elf *elf, struct section *sec, 
	sec = sec->rela;



	for_offset_range(o, offset, offset + len) {

		hash_for_each_possible(elf->rela_hash, rela, hash,

		elf_hash_for_each_possible(elf->rela_hash, rela, hash,

				       sec_offset_hash(sec, o)) {

			if (rela->sec != sec)

				continue;
@@ -309,8 +325,8 @@ static int read_sections(struct elf *elf) 
		sec->len = sec->sh.sh_size;



		list_add_tail(&sec->list, &elf->sections);

		hash_add(elf->section_hash, &sec->hash, sec->idx);

		hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));

		elf_hash_add(elf->section_hash, &sec->hash, sec->idx);

		elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));

	}



	if (stats)
@@ -394,8 +410,8 @@ static int read_symbols(struct elf *elf) 
		else

			entry = &sym->sec->symbol_list;

		list_add(&sym->list, entry);

		hash_add(elf->symbol_hash, &sym->hash, sym->idx);

		hash_add(elf->symbol_name_hash, &sym->name_hash, str_hash(sym->name));

		elf_hash_add(elf->symbol_hash, &sym->hash, sym->idx);

		elf_hash_add(elf->symbol_name_hash, &sym->name_hash, str_hash(sym->name));

	}



	if (stats)
@@ -456,6 +472,14 @@ err: 
	return -1;

}



void elf_add_rela(struct elf *elf, struct rela *rela)

{

	struct section *sec = rela->sec;



	list_add_tail(&rela->list, &sec->rela_list);

	elf_hash_add(elf->rela_hash, &rela->hash, rela_hash(rela));

}



static int read_relas(struct elf *elf)

{

	struct section *sec;
@@ -503,8 +527,7 @@ static int read_relas(struct elf *elf) 
				return -1;

			}



			list_add_tail(&rela->list, &sec->rela_list);

			hash_add(elf->rela_hash, &rela->hash, rela_hash(rela));

			elf_add_rela(elf, rela);

			nr_rela++;

		}

		max_rela = max(max_rela, nr_rela);
@@ -531,15 +554,16 @@ struct elf *elf_read(const char *name, int flags) 
		perror("malloc");

		return NULL;

	}

	memset(elf, 0, sizeof(*elf));

	memset(elf, 0, offsetof(struct elf, sections));



	hash_init(elf->symbol_hash);

	hash_init(elf->symbol_name_hash);

	hash_init(elf->section_hash);

	hash_init(elf->section_name_hash);

	hash_init(elf->rela_hash);

	INIT_LIST_HEAD(&elf->sections);



	elf_hash_init(elf->symbol_hash);

	elf_hash_init(elf->symbol_name_hash);

	elf_hash_init(elf->section_hash);

	elf_hash_init(elf->section_name_hash);

	elf_hash_init(elf->rela_hash);



	elf->fd = open(name, flags);

	if (elf->fd == -1) {

		fprintf(stderr, "objtool: Can't open '%s': %s\n",
@@ -676,8 +700,8 @@ struct section *elf_create_section(struct elf *elf, const char *name, 
	shstrtab->changed = true;



	list_add_tail(&sec->list, &elf->sections);

	hash_add(elf->section_hash, &sec->hash, sec->idx);

	hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));

	elf_hash_add(elf->section_hash, &sec->hash, sec->idx);

	elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));



	return sec;

}

tools/objtool/elf.h

+8 −5
Original line number Diff line number Diff line
@@ -70,17 +70,19 @@ struct rela { 
	bool jump_table_start;

};



#define ELF_HASH_BITS	20



struct elf {

	Elf *elf;

	GElf_Ehdr ehdr;

	int fd;

	char *name;

	struct list_head sections;

	DECLARE_HASHTABLE(symbol_hash, 20);

	DECLARE_HASHTABLE(symbol_name_hash, 20);

	DECLARE_HASHTABLE(section_hash, 16);

	DECLARE_HASHTABLE(section_name_hash, 16);

	DECLARE_HASHTABLE(rela_hash, 20);

	DECLARE_HASHTABLE(symbol_hash, ELF_HASH_BITS);

	DECLARE_HASHTABLE(symbol_name_hash, ELF_HASH_BITS);

	DECLARE_HASHTABLE(section_hash, ELF_HASH_BITS);

	DECLARE_HASHTABLE(section_name_hash, ELF_HASH_BITS);

	DECLARE_HASHTABLE(rela_hash, ELF_HASH_BITS);

};



#define OFFSET_STRIDE_BITS	4
@@ -127,6 +129,7 @@ struct section *elf_create_rela_section(struct elf *elf, struct section *base); 
int elf_rebuild_rela_section(struct section *sec);

int elf_write(struct elf *elf);

void elf_close(struct elf *elf);

void elf_add_rela(struct elf *elf, struct rela *rela);



#define for_each_sec(file, sec)						\

	list_for_each_entry(sec, &file->elf->sections, list)

tools/objtool/orc_gen.c

+1 −2
Original line number Diff line number Diff line
@@ -130,8 +130,7 @@ static int create_orc_entry(struct elf *elf, struct section *u_sec, struct secti 
	rela->offset = idx * sizeof(int);

	rela->sec = ip_relasec;



	list_add_tail(&rela->list, &ip_relasec->rela_list);

	hash_add(elf->rela_hash, &rela->hash, rela_hash(rela));

	elf_add_rela(elf, rela);



	return 0;

}

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